Sunscreen buying guide: SPF, broad spectrum and finish explained

Sunscreen is one of the few skincare products with strong, consistent public-health guidance behind it. Most of the confusion is about labels and texture, not whether to use it. This is general educational information, not medical advice. If you have a skin condition or concerns about moles, talk to a doctor or dermatologist.

What SPF means

SPF (sun protection factor) describes protection against UVB rays, the main cause of sunburn, under standardised test conditions. A higher number gives more protection, with diminishing returns: SPF 30 filters roughly 97 percent of UVB and SPF 50 roughly 98 percent. In practice, how much you apply and how often you reapply matters at least as much as the number.

Health agencies commonly recommend SPF 30 or higher, applied generously.

Broad spectrum and PA ratings

UVA rays contribute to skin ageing and also to skin cancer risk. “Broad spectrum” on a label (in the US) means the product passed a test for UVA protection proportional to its SPF. In Asian markets, PA ratings (PA+ to PA++++) describe UVA protection, and in the EU a UVA logo (a circled “UVA”) indicates a minimum UVA ratio.

Look for broad-spectrum protection regardless of where you shop.

Mineral versus chemical filters

Neither category is automatically “safer”. Regulators approve specific filters; availability differs between regions, which is why formulas vary across markets.

How much to apply

The tested SPF is based on a generous application, about 2 mg per square centimetre of skin. Most people apply less, which reduces real-world protection. A common guide is roughly a teaspoon for the face and neck, and enough to coat the exposed body. Reapply about every two hours, and after swimming, sweating or towelling.

Water resistance and other claims

• Water resistant labels state how long (for example 40 or 80 minutes) protection holds in testing. They do not mean waterproof.
• “Sunblock” is not a permitted claim in some regions, since no product blocks all rays.
• Reef-safe has no universal standard; check the specific filters if this matters to you.

Finish and fit with your routine

You will use a sunscreen you like. Consider:

• Skin type: gel and fluid textures suit oily skin; creams can suit dry skin.
• Under makeup: thin, quick-absorbing formulas layer better.
• Tint: tinted mineral options reduce white cast.
• Fragrance: fragrance-free is safer if your skin is reactive.
• Format: sticks and sprays are convenient but make it easier to under-apply; follow the instructions for coverage.

Special cases

Children. Health agencies advise keeping babies under six months out of direct sun and using protective clothing and shade; ask a paediatrician about sunscreen for infants. For older children, choose a broad-spectrum formula and reapply often, especially after swimming.

Sensitive or acne-prone skin. Fragrance-free and mineral formulas are often better tolerated. Patch test, and look for non-greasy textures. If a product stings your eyes, try a stick or a different filter combination.

Darker skin tones. Sunscreen is still important. Tinted mineral formulas or fluid chemical formulas can reduce the chalky look some mineral filters leave.

Makeup and reapplication. Reapplying over makeup is awkward. Options include a spray or powder with SPF for touch-ups, though these are less reliable than a generous layer of cream, so do not rely on them as your only protection.

Storage and expiry

Heat and sunlight degrade sunscreen. Keep it out of hot cars and direct sun, close the cap, and replace bottles that have separated, changed smell or passed their expiry. Most products show an open-jar symbol with a number of months after opening.

Choosing: a quick checklist

Questions readers ask